The overall goal of Project 3 of the Research Program is to chemically define oxidative pathways that participate in the initiation and propagation of the inflammatory responses in asthma. Leukocytes play an essential role in the body, destroying pathogenic microorganisms and tumor cells. They also have great potential to harm healthy tissue. Because oxidative damage is cumulative, this potential is enhanced in chronic inflammatory diseases like asthma. We have used mass spectrometry to show that eosinophils and neutrophils, via their respective unique heme peroxidases, eosinophil peroxidase (EPO) and myeloperoxidase (MPO), promote protein oxidative damage in human asthmatic airways. Recent studies also suggest an important role for lactoperoxidase (LPO), a related member of the heme peroxidase superfamily, in maintenance of airway innate immune defenses. The present proposal is predicated upon the hypothesis that oxidative reactions, such as those mediated by redox-active transition metal ions, nitric oxide-derived oxidants, and mammalian heme peroxidases, affect acute and chronic features of the disease process, including airways remodeling. Our evidence suggests mechanistically distinct oxidative pathways promote structurally definable alterations to lipid and protein components of the bronchiole wall in asthmatic airways. We propose to integrate studies on basic mechanisms with a search for specific reaction products that reveal whether relevant pathways operate in animal models of pulmonary inflammation and in human asthma. We will use murine models to define specific enzymatic participants that contribute to formation of specific bioactive eicosanoids, protease resistant covalent cross-links, and other defined oxidative modifications in lung and airways following allergen challenge. With Project 2 we will explore the role of extracellular matrix on modulating defined oxidative processes in asthmatic airways. Through human clinical investigations and collaborations with Project 1 we will explore the potential clinical utility of specific structurally informative oxidative adducts as non-invasive markers for disease presence, severity, pulmonary function, and the extent of airways remodeling. All cores are extensively used by this Project. Collectively, the proposed studies will provide insights into oxidative processes participating in inflammatory injury and remodeling in asthma.